Branch heads should not include "heads" that are ancestors of other heads.
For example, given 1 (branch a) -> 2 (branch b) -> 3 (branch a)
I expect "hg heads a" to show only 3.
Discovered by running hg heads HEAD on the mutt repo, where older clients
committed default on top of HEAD.
#!/bin/sh
# Just exercize debugindexdot
# Create a short file history including a merge.
hg init t
cd t
echo a > a
hg ci -qAm t1 -d '0 0'
echo a >> a
hg ci -m t2 -d '1 0'
hg up -qC 0
echo b >> a
hg ci -m t3 -d '2 0'
HGMERGE=true hg merge -q
hg ci -m merge -d '3 0'
hg debugindexdot .hg/store/data/a.i